Gun stabilizing apparatus



Aug. 7, 1945. L. B. LYNN 2,381,161

GUN STABILIZING APPARATUS Filed Nov. 25, 1940 2 Shee' tS-Sheet 1 awrqc zygz WMAW 7 ATTORNEY 1945- B. LYNN 2,381,161

GUN STABILIZING APPARATUS Filed Nov. 23, 1940 2 Sheets-Sheet 2 y l q WITNESSES:

INVENTOR BY FMZrMW ATTORN EY ,ing the gun at a predetermined Patented Aug. 7, 1945 2,881.,llill GUN s'ram lilawrenoe E. 1 'Wmtinghouse Electric.

a. as, Pa... assigns? o Corporation, Ziaet'mttse v burgh, Pea, a corporation of'l'ennsylvania V Application November 23, 1940, Serial at. 866.9153 2 (or. 89-41) My invention relates to a control system for maintaining an element, such as a gun, at a prebe used to maintain any element at a predetermined position with respect to sensing means such as an artificial horizon."

.with respect to a distant target. The invention in said copending application is especially adapted to control the movements of a gun which is pivotally mounted in a tank so that the gun,

once aimedat a distant target, will maintain its aim or be continuously trained on such target, irrespective of vibrational or other disturbing movements'of the tank in the course of its movement towards the target. It is w'ellknown' that a tank in the course of its movement will pitch and roll. Pitching movements are movements about an axis at right angles to the direction of My invention, however, is particularly adapted to a gun mount including a system for maintainposition with respect to an fartiflcial horizon."

An object of my invention is to provide a con-I trol-system for controlling the movements of a gun with respect to a pivotal support therefor, which control system will be unaiiected'by recoil.

movements of the gun. *A more specific. object is'to provide, in addition to the control system for maintaining a gun or otherbbiect at a made? termined angular relation with respe'ctto an "artiiicial horizon suchas shown and claimedin said copending application, a means to render said control system unaffected by the recoil movements of the gun. sons to maintain control of the gun at all times.

Other objects and advantages will become 'mor'e apparent from a study of the following specification when considered in conjunction with the accompanying drawings; in which:'

Figure l is a perspective view shown partly. broken away, of a recoil switch forming part of.-

my invention as applied to a sun which is mounted on a tank;

Fig. 2 is a perspective view of a unit includins a gyro vertical, a Silverstat, an" anticipation gyro, and a. bellows;

Fig. 3 is a schematic showing'partly in cross section. and an electrically controlled hydraulic system. involving the principles ofmy invention; and

Fig. 4 is a cross sectional view taken along the line IV-IV of Fig. 2 showing the bellows structure.

The artificial horizon or gym vertical described and claimed in said copendingapplication may serve as a sensing means in connection with my invention since it is an index means which will continuously indicate the direction of the center of the earth. Therefore, it may form a basis upon which an object finding arrangement, such as a gun, may bemounted in proper position vention, will now be described for the sake of detravel of the tank while rolling movements are movements about an axis parallel to the direction of travel.

Figure 1 shows a gun mounted on atank together with means for correcting for pitching disturbances, but which do not correct for rolling disturbances. Such gun is pivotally mounted for movement about only one axis, which permits adjustment only of theelevation of the gun.

The artificial horizon" or gyro vertical device,

per se, while forming no partof my present inscribing a completely operative device.

Referring to Figs. 1 and 2, numeral i denotes a support which; as will appear more clearlyfllater, is adjustably flxedwith respect to the gun, and which willpartake of the pitching movements of the gun. Numeral 2 designates a bracket which is rigidly mounted on support I and whichhas pendulously mounted thereon a U-shaped pendu- -lous member 3. In other-words, pendulous memher "I is adapted to freely revolve about bearings on the Z axis. 'It will be readily. apparent that if support iwere to be gradually tilted in its own plane, thependulous member 3' would tend; at all times, to align itself with the center of the earth due to the gravitational forceexerted thereon by such center of. the earth. However, if suchtilting movement of support I were violent or if such supp rt were to have a vibratory movement of medium or high frequency; pendulous member 3 would be quite unstable and would tend to'oscillate tosuch anextent that.

it could no longer be reliable as'a meansfor indicating the direction of the earth's. center.

In order .to stabilize the movement of 'pe'ndulous member 3, a gyro vertical is provided which comprises a gimbal ring 4 pivotally mounted on bracket '2 so that it will be rotatable about the 'z-axis and a block I which is rigidly clamped about a motor housing I and which is pivotally supported by a gimbal ring 4 along the X-axis which 18 the axis of precession. A motor denoted generally by M is located within housing 8 and drives a fly wheel I which constitutes a gyro wheel. Since such gyro wheel I has a vertical axis (or Y axis) and since the motor housing is pendulously mounted in gimbals, the gyro wheel will inherently and gradually seek a vertical, that is, seek alignment with the earth's center. If there were no friction in the universal gimbal mount, however, the axis of the gyro wheel would oscillate in a oonical'path indefinitely, once its axis is til-ted from the vertical, such as would be effected by rocking movement of the gimbal ring 4 about the Z-axis. This rocking movement, of course, could be caused by sudden stopping, or accelerating movements of the tank, or by movements of the tank while going over rough terrain. Friction at the gimbal hearings or any other resistance to such conical vibration tends to precess the gyro wheel axis back to vertical -m a spiral path. Constant friction, however,

is highly undesirable because it prevents a complete return of the gyro wheel axis to its normal, earth's center pointing position. I provide a frictional damping means in the form of a track 8 formed by two longitudinal members arranged to turn about axis Z, the motor, its housing, and.

fly wheel i would all rock 'or precess about the X-axis, thereby causing a precession movement of stud 9 along track 8. The bracket member ID is pushed sidewise in a sinusoidal manner by the pendulous member 3. The force of the pendulous member 3 against stud ii is proportional to its deflection from vertical. It will, therefore, be seen that the sliding friction is proportional to this and the force is maximum when the sliding velocity of stud 9 along track 8 is greatest. Therefore, if the gyro wheel axis is at the normal earths center pointing position, the friction approaches zero. Consequently, there is no error arising from this type of damping. The damping will be in wholly one plane, the plane defined by axes X and Y. The gyro wheel axis will spiral inwardly in an unsymmetrical manner, that is,

prising a plurality of flexible metallic leaves I! which carry contact members I, preferably made of silver. The contact members II are arranged in a pair of groups with'the contact members of the respective groups connected along spaced taps of the resistors i6 and ISa.

While a normal operation of contacts would be to maintain the contacts normally in their own position,. prefer, in accordance with my invention, to have at leastone pair of contacts on each side of the actuating element [8 normally I closed so as to effect opening of such contacts on one side while the other contacts are being closed Fig. 1, as support I tilts counterclockwise, within not of the form of an eliptical spiral with its the specific application shown in Fig. 1, namely,

the Z axis, the smaller stability about'the X-axis has no effect on the performance of.the device shown.

As has been explained before, any pitching movement of the tank'which corresponds to movement of support I within its plane, it sumciently sudden, will cause a rocking movement of the motor and gyro wheel about axis X or in other words, a precessional movement of stud 9 along track 8. The greater the amount of rocking movement of gimbal ring 4 the greater will be the degree of precessional movement of stud 9 along the track 8 and the greater will be the resistive force exerted by the track .to tend to returnits own plane, it will allow the pendulous member 3, together with the contacts carried thereby to move through an angle 0 with respect to the contact actuating element l6, hence, wouldeflect a progressive shunting of the right-hand contact members M. 01 course, upon movement of the contact actuating element IS in an opposite direction, clue to opposite movement of the support, there will be progressive shunting of the lefthand contact members.

The mere provision of a means responsive todisplacement only of the disturbing movements is insumcient and unsatisfactory for most purposes since it is accompanied by sluggishness and since there is a significant amount of hunting which makes the system relatively unstable. In Order to overcome this dimculty, there is used a second gyroscope referred to as an anticipating gyro, since it is responsive to the velocity of movement of support i, that is, to the velocity of the disturbance. Such anticipating gyro performs an anti-hunting function, as will be apparent from the following description, Rigidly mounted on support I is a substantially U-shaped bracket I! which pivotally supports a block i8, which block is rigidly secured about housing I! which encloses the second or anticipation gyro motor, which drives gyro wheel 20. Rigidly mounted on .the face of block I8 is the contact actuating element I6.

Assuming a clockwise movement of support I, it will be apparent that contact actuating element l6 will be moved clockwise about the disturbance axis, namely, the axis about which the gun 2| is pivoted, which axis extends through the trunnion 22. The anticipation gyro is so mounted that the axis of gy o wheel M will precess about the Y-axis through an angle which is proportional to the velocity of movement of support I. In other words, if the error of displacement by the actuating element l6 and the contacts is denoted by 0 (or 0') then the angular precession of the lower gyro is denoted by 02 which is proportional to the rate of change of error anticipation gyro so as to have an opposite effect on the contacts that is, if the displacement tends to close the contacts, the anti-hunting force will tend to open them. Veloc ty precedes displacement in point of time, velocity tending to be a maximum when displacement tends to be a minimum and vice versa. Velocity sense and displacement sense are in the same direction when departing from a position of equilibrium, with the result that velocity and displacement operate to oppose departure, velocity providing a strong force opposing displacement before any appreciable displacement has occurred and thereby contributing an anticipating effect. On the other hand, with displacement having the same sense and decreasing, velocity having reversed incident to displacement having passed through a max mum, the velocity sense is reversed with the result that velocity provides a force oppos ng return as equilibrium is approached in order to minimize overtravel and hunting. In this manner, a very quick responsive sensing device is provided which is practically free from hunting, therefore, which is extremely smooth in operation and immediately responsive to movements of support or movements of the gun 2|.

In order to provide dam-ping to the movements of actuating element I6, a rigid pin 23 is clamped at the bottom end thereof which pin extends to a flexible spring-like element 24 rigidly supported on support The left-end of such flexible spring-like element 24 is secured to the casing of a small bellows 25, which bellows is in communication with another slightly larger bellows 26 through a duct or passage 21, as shown in Fig. 4. Both bellows are preferably filled with a fluid such as a liquid, for example, oil, so that movements of actuating element I6 will be damped by alternate expansive and contractive movements of bellows and .26 as fluid is passed from one to the other through passage 21. Such damping means also forms no part of my present invention.

Fig. 3 shows in a schematic way the operation of the entire system. A current is furnished by battery 28 or other source of energy which is normally equally divided between the right-hand and left-hand portion of resistor I5 since it forms two parallel paths extending, respectively. through actuating coils 29 and 30. Two valves 3| and 32 are interconnected by a common valve actuating element 33 pivoted at 34, both valves being normally open because of'normal equal energization of coils 29 and which actuates the poppet or seated type valves 3| and 32. Under balanced condition, a motor M drives pumping means ineluding a pair of pumps 35 and 35a. Such pumps are diagrammatically indicated as being constituted by reversely-threaded propeller blades carried by the motor shaft with a c'ommoninlet between the blades and with outlets at the outer ends thereof, as indicated by arrows in Fig. 3. Two separate closed paths are indicated by arrows between each of the pumps and valves 3| and 32, respectively. Tapped on the upper closed path, that is, the one normally going through valve 3|, is a pipe line 4| which is connected to the upper space in a cylinder 38 which cylinder is rigidly secured to bracket 42 which, in turn, is rigidly secured by.pins 43 and 44 to stationary parts 45 and 45a of the frame of the tank indi-- cated in cross section. Similarly, tapped on the vation or at a predetermined position with respect to the bracket 42 or the frame structure. A leakage lead line 12 is connected to the intake pipe and leads directly through the packing through which the piston rod reciprocates and leads directly to such load so that as excessive pressure is developed in the upper part of the piston chamber, excess oil will be able to leak into pipe 12 instead of forcing its way throug the packing seal. 1

The chamber 36 which encloses such valves and plunger type electromagnetically operated valve operators may constitute a sump or reservoir or may have attached thereto an additional sump or reservoir (not shown) if so desired.

Assume that the right-hand resistor l5 has been partially shunted by the contacts due to relative movement of actuating element l6 and the flexible contacts as the result of rocking movement of support with the gun of Fig. 2 in a counterclockwise direction. It will be seen that more current will flow through coil 29 due to the decrease of resistance in series therewith, than through coil 30 which will effect counter-clockwise movement of valve actuating arrangement 33 which will result in movement in a closing direction of the lower valve 32 and further opening movement of upper valve 3|. Asa consequence of this, the pump will build up consider able pressure in the pipe line 31 which will cause a large pressure increase at the bottom of cylinder 38 which will cause an upward movement of piston 39 therein, which, in turn will effect an upward push on joint 4|] which is. secured to the gun 2| causing aclockwise movement of the gun about its trunnion or pivot 22.

If, on the other hand, the displacement were in the opposite direction so that the left-hand instead of the right-hand portion of resistor 5 were shunted, coil 30 would be energized to a greater. extent than coil 29, causing movement in a closing direction of the upper valve 3| and building of pressure in the pipe line 4| and in the space above the piston 39 with the result that the piston would, be actuated in a downward dipects of my invention will more clearly set forth the advantages inherent in my system.

The hydraulic pressures in the stabilizer cylinder are controlled by their respective valve currents. As the currents and magnetic flux densities are increased, negative stiffness is also increased. Regarding the definition of stifiness, a body is said to have positive stiffness if its resistance increases upon compression, such as is inherent in a spring. An electromagnet has negative stiffness, since, as the armature is attracted toward the core, a smaller and smaller force is required. If such negative stiffness becomes greater than the positive stifiness arising from the hydraulic pressure on the valves, unstable operation occurs. The range of instability may be varied by changing the valve clearances, air gaps or other constants, and may be kept low by keeping the total valve currents at a minimum.

Valve operation with a fixed current in one coil and a variable current in the other, as described by C. R. Hanna in said copending application, requires rather substantial fiux densities so that the range of unstable operation is appre ciable.

By reducing the current in one valve operating electromagnetic coil as the current in the other coil is increased (class A push-pull) the average flux is reduced and stability is improved.

Another method of operation comprises the provision of two sets or groups of contacts one on theright and the other on the left of the actuating member with all of the contacts normally in the open position. Since at any instant only one side of the valve need be operative, it is nec essary for current to flow in but one coil at a time. This type of operation (class B push-pull) further reduces the average flux density and greatly improves the stability.

Push-pull operation such as involved in either class A or class B described above on the gun stabilizer has been obtained by employing two sets or groups of contacts as shown in Figures 1, 2 and 3. The broad terminology of push-pull operation of the gim should be distinguished from the specific terminology "push-pull operation as applied to the variable resistors per se.

Push rod or contact actuating element l6, of insulating material, is attached to one element of the gyroscopic position sensing device, and the groups of contacts, are attached to the other element. A change in position of the gun causes more leaves of one group of contacts to be closed, or fewer of the other group to be closed, or both.

By choice of the length of the push-rod IE, it is possible to obtain any of several classes of pushpull operation. Class A appears to be preferable since the contacts are immediately responsive to the slightest movementof the actuating element I 6 from its normal central position.

It is desirable to have equal increments of corrective torque for equal increments of angular displacement of the gun. As applied to the gun stabilizer, for example, 15 contact leaves may close for 1 angular displacement of the gun, or 1 leaf for each 4. The pressures as controlled by the valves are approximately proportional to the square of the valve currents, being distorted by pump characteristics and other factors. Ac-

tual graphs of corrective torque against valve curculated. Resistors l5 and I50. in Figure 3 were made with steps of these values and connected to their respective groups of contacts leaves.

Thus a linear relation between angular gun displacement and restoring torque is obtained. The rate of change of torque to displacement, or the stiffness of the stabilizm', is determined by the voltage applied to the circuit and may be varied by means of the potentiometers 16 and 11. Such potentiometers allow independent adjustment for each coll actuating circuit.

During recoil following firing of the gun, excessively large unbalance torques exist because of the displacement of the center of gravity to a position to the rear of the trunnion, for periods of about one-half second. Because these unbalances occur only after each shot and persist for relative short periods, and because of space and weight limitations imposed, it is undesirable to build the stabilizer large enough to accommodate these large disturbances, which are many times the magnitude the disturbances transmitted to the gun from the motion of the vehicle.

In accordance with my invention, I avoid the necessity of building such a large stabilizer as would be necessary in the system shown and claimed in said copending application of C. R. Hanna. By supplying a high current to the associated valve coil during recoil, the gun is closely coupled to its mount and supported during this period of unbalance. The high value current may be supplied by an additional voltage applied to the coil circuit by the auxiliary coil 13 through a switch 14 operated by the motion of the gun undergoing recoil. In this manner additional energization is provided which tends to close the lower valve, resulting in building up of pressure in the cylinder below the piston which counteractsthe pressure created by downward movement of the piston as a consequence of recoil unbalance of the gun. A check valve 18 normally biased to its closed position by a spring may be provided for the purpose of preventing the backward flow of fluid through the pump when the pressure created by the downward movement of the piston becomes in excess of the peak delivery pressure of the pump.

Fig. 1 shows more clearly the actual construction indicated somewhat schematically in Fig. 3. As will be noted, the housing which encloses the two pumps, namely housing 66, and the valve chamber 36 are secured together for the sake of providing a compact unit, although, it will be readily understood that they may be separated if so desired. Fig. 1 shows more clearly how pins 43 and 44 are rigidly secured to parts of the tank frame, broken sections of which are indicated by numerals 45 and 45a. It will, therefore, be seen that bracket 42 which supports the trunnion 22 of the gun is rigidly secured to the frame structure of the tank. Bracket 42 together with the bearing member 46 forms a support for the gun 2| and its associated structure so that the gun will be free to move in a vertical plane so as to make its elevation adjustable but which will restrain movements in a horizontal or lateral plane. With such construction, the operator of the tank is relied upon to drive the tank in the direction of the target at.

all times so that in such manner, lateral deviations will be compensated for ina degree commensurate with the operator's ability to steer directly towards the target at all times. The gun 2| has an inner bracket 41 secured at the lower end thereof to the recoil chamber 48, which bracket has integrally connected thereto the trunnion 22.

In order to make it possible to adiustthe elevation of the gun, I show the same system shown and claimed by said copending application 01 C. R. Hanna. A handle 49 is provided and which is supported by a bracket 50 rigidly mounted on the recoil chamber 48 and having a portion to which is rigidly mounted a shaft 5|. As handle 49 is rotated, it rotates ,a worm wheel 52, which,-

in turn, rotates a shaft 53 which has a gear 54 and'worm 55 attached to respective ends theretherewith the entire gear system, including the elements 52-54-55-58.

If it is desired to elevate the gun directly, that is, without resorting to the amplifying force proof, and which drives a gear 56 through the worm 55. A substantially Z-shaped bracket 51 rigidly secures gear 56 to support i. It will be noted,

, therefore, that, by cranking handle 49, support I is turned about the axis of shaft 5|. With each increment of turning movement of handle 49, the pendulous member 3 of the'upper or vertical gyro will be swung from its normal position, that is, will be swung from the position at which left and right-hand contacts of the Silverstat allow insertion of full and equal values of resistance on the left and right-hand portions of resistor i5. However, as soon as support I is tipped in such a direction so that either the left or right-hand set of Silverstat contacts are gradually shunted, either coil 29 or coil 30 will be energized so as to eilect movement in a closing direction of one of the valves 3! or 32 so as to cause either upward or downward motion ofthe piston 39, which, in turn will cause clockwise or counter-clockwise movement of the gun 2| in the manner previously described. In other words, the turning of handle 49, which can be done with very little force, since it is connected only to the support I and its associated gyro structures, provides a means for controlling the elevating movements of the relatively heavy gun by controlling the pressures on the respective sides of the piston 39. In other words, the hydraulic system serves as a power amplifier for the manual movements of the crank 49. With each increment of turning movement of crank 49 resulting in turning movement of support I and of the relative movement of the actuating member I 6 and the contacts, there will be a hydraulic force developed tending to move the gun in such a direction so that it will always maintain a predetermined angle with respect to the plane of plate II or it may be said that it will always maintain a predetermined angle with respect to the normal gyro vertical spinning axis X. Since shaft 53 is rigidly supported to the gun by virtue of brackets 58 and 59, and since gear 59 is rigidly connected to the gunby virtue of shaft 5|, it will be apparent that as the gun rotates about its trunnion 22, it will carry vided by the stabilizer system, the elevation mechanism indicated generally by numeral 60 may be used instead, which elevation mechanism is well-known in the art comprising essentially a worm 6f which is mounted in a housing 62-which is swingable about a shaft 63, so that it can be moved into or out of engagement with an arcuate gear segment 64 rigidly supported to the gun. By turning the handle 65, the gun may be elevated through the driving engagement of worm BI and the gear teeth on the arcuate gear segment 64. This means of elevation is not useable, of course, when the stabilizer action i desired.

While the contact leaves l3 are shown as being tapped along resistors l5 and We, it will be understood that such contact leaves might be tapped along any suitable impedance elements.

I am, of course, aware that others, particularly after having had the benefit of the teachings of my invention. may devise other devices embodying my invention, and I, therefore, do not wish to be limited to the specific showings made in the drawings and the descriptive disclosure hereinbefore made, but wish to be limited only by the scope of the appended claims.

I claim as my invention:

1. In combination with a trunnion-mounted gun and an automatically-controlled liquid pressure system for positioning the gun about its trunnion axis, means providing for utilization of said system to oppose angular movement of the gun due to unbalance thereof brought about by recoil, and means responsive to recoil motion of the gun to render said means eifective.

2. In combination with a trunnion-mounted gun whose angular position about its trunnion axis is controlled by liquid pressures applied to oppositely-directed areas of means operatively connected to the gun and wherein the pressures are controlled by a pair of valves operated by an electrical system which is responsive to angular motion of the gun about the trunnion axis, a circuit forming a part of said electrical system, magnetic means operative to move one of said valves in a closing direction to provide liquid pressure acting on a pressure area to oppose angular motion of the gun about the trunnion axis due to unbalance thereof brought about by recoil, said magnetic means including'a winding forming a part of said circuit, and a normally-open switch included in said circuit and closed in response to recoil motion of the gun.

LAWRENCE B. LYNN. 

